Dressing device for grinding wheels



Jan. 13, 1948. w. w. HOPKINS DRESSING DEVICE FOR GRINDING WHEELS FiledMa y 1'7, 1945 BY a 9 6 ATTORNE JS Patented Lian. 13, 1948 UNI-TEDSTATES GP'FICE V 23134516 I nRiassiNG DEVICE. FOR GRINDING WHEELSWilliam Walter fiopkins, Springfield Mass. ApplicationMay 17, 1945385211se il'sslz 'oiaiiils. (o1. 125 113 This invention relates 'to'animproved'dressing device for grinding wheels.

In the prior practice, an industrial diamond is mounted in asupport,'the grinding wheel is rotated, the diamond is;moved jback andforth on a'curve, corresponding to the cross sectional shape of adesired dressing, the wheel'and dia- 'mond are moved against each otherby'small steps, and the diamond; grooves the wheel step by-wstep untilthe desired "formds made. The

:form is an annular groove having'a precision cross sectional-shape..This is allvery well known.

In some kinds of Work,"a special problem is. presentedto thekilled-man'wanting to dress a wheel to-a shapei thatis notadapted to bemade by the most usual. method, For example, the dressing of a smallgroovexto be. made in'the grinding wheel, with a semi-circular crosssection having aa s inch radius presentsa special problem. The radius istoo small to use'the most usual dressing method. When" precision isneeded in such an"instance,one Way to get it is to shape a diamond forthe desired cross sec tional curve and press the shaped tool (diamond)radially against the grinding .wheel. to dress the latter. It is anexpensive Wayand'not. only that, it is far from a convenientwayibecaus'e such a small andexpensive. tool quickly gets defective.

The diamond even when welded to'itsiholder snaps off after little useand the precision shape is worn away after little use.

With these circumstances as a background, I have invented a new andinexpensive device to do the work t dressin g;= Itsis particularly adapted to convenience and precision in making dressings of small crosssectional shapes as in the specific example already given, and it isalso adapted-for making dressings of comparatively large cross sectionalshapes.

The new device, its mode of operation and the.

results will be disclosed and referred to in connection with theaccompanying drawings,

Fig. l isaside view of the device andindicates the relationof the workto the cutting diamond" and a way of feeding the work in the operation;,

Fig. '8 is a section "taken" along thefsam' line as Fig'."5 but with theparts in ene extreme position;.an'd' w 3 L Fig'fiis an'en'd viewgthe meas FigQZQwith parts broken'awa'y The iull lin position shows the war suport against a 'st'opand the diamond point scribing an afiz in 'agrinding' wheel, partially shown, and the dpttedlines'ShOW the am;

and its tOOYsuppOrt aga st a stop to prevent it from hitting nie rmdin xr ln the exarnpl'e'bftheinvention' shown by these drawings': v

. The diamond icutting' elem t"'l 'is'-vve lded' on the end ofiholdingrod 2; This is snaab y incune ed for? adjustment in? anoth'e'fholding"rod 3, the

IO... extends rearwardly through bore H andbe-g At .itsrea'r end acollar l2- w. isjastened by set .scr'ew'sl3fi The collar l2 and Thecollar' I2- is part of a. ,frictionclutch. T This clutch is made up of,collar, 1.2 which -on. its inner face}. has 'an yond ,the'cylinder l.

the shaft [0 must move'togeth'er.

annular. series. of recesses .and' in. each recess a coiledi spring"is-jbotto'medlThe' springs press .on its. outer face engaged withopposite holes on the inner iface. ofcollar [2... Thus the disc'iun'derspringpressiire may move .jaxia'lly of. shaftilfl between ciolla'rl,2.'and the adjacent face ofsfrarnel part 8, and both clutchpiartsmusti turn withshaft ID lutch is assembled ,and. mounted;asindicated, so. that. therer-is; considerable friction tojthe turnin ofshaft 1.0. in cylinder 1 because of the clutch parts. which turnwith therod. 'The" it'an'd slide relatively,being feathered. on theshaft.forjthis purposa- DiscJI4..has.two pins. l4

friction is. between disc 1.4 and frame 8.

outer position but permitting .it to be'pushdin wardly.j.,A.r'ada1V;shaped.-grdove. L6,. on the innerl. .face oLdisc l4, cooperates withpin [5, as will be described.

A handle H, in the form of a radius rod fastened to cylinder 1, andextending through the slot shown in the frame 8, see Fig. 1, providesmeans for rocking the cylinder 1 in its frame bearing and such rockingis back and forth about the cylinder aXis.

As stated before, shaft II] is carried in the eccentric bore ll ofcylinder I. So, when the cylinder 1 is rocked back and forth by handleI1, the rocking axis being the cylinder axis, then shaft ill will haveits axis moved back and forth over an are whose radius is the amount ofthe eccentricity or offset of the shaft I axis with the cylinder axis,This is indicated by the center lines in Fig. 1 and the centers in theother figures.

With the construction so far described, one grinding wheel dressingoperation will be described. The diamond l is adjusted so its cuttingpoint coincides with or is on the axis of shaft I0 and fixed there. Aflat portion on the upper side of block 6 adjacent its end may be made aprecision base for setting the diamond point to this adjustment. It isdesired to provide for great precision in the setting stated. The handleI! may have a line to coincide with a line on frame 8 when the handle isexactly vertical, at which time the rod 2 holding the diamond is alsovertical, detent groove I6 is vertical, and detent IE is in its groovel6. At this time the axis of shaft I0 is set above axis of cylinder 1and on a vertical line passing through both axes. This is the startingposition of the device. When the device is set in this position, thegrinding wheel to be dressed is moved down by adjustment of the workholder H indicated in Fig. 1, until the diamond is just touching theperiphery of the grinding wheel. It is from this position that thegrinding wheel will be fed, by indexing feeding means, indicated at I,to move the work toward the tool (diamond) in precision steps, forexample steps of five thousandths of an inch each. The result of thepreparation setting of the work and the tool for operation is indicatedgenerally in Fig. 1. It will be understood that means not shown willrotate the grinding wheel.

From the preparation just described the operation will be to move thetool in an arc away from the work by turning the handle l1. Then thework holder moves the grinding wheel down with a precision step. Thegrinding wheel is rotated. Then the handle I! is rocked to swing thetool against the work and back and forth, in an arc. This are has aradius equal to the offset of shaft ID from axi of cylinder 1. Thediamond will dress an annular groove in the wheel with depth equal tothe precision measurement of one step in feeding the work against thediamond. This of course assumes that the grinding wheel has a fiatperiphery to start the sinking of a groove in it. Between each twofeeding working steps of the work holder, handle I1 is rocked enough todress an annular groove to the depth of one feeding step. Of course thedepth of the groove will gradually increase with the addition of eachfeeding step and the following dressing step. If we assume that theradius of the arc in which the diamond is swung in each such dressingstep is a large enough radius, the whole dressing of the groove mayproceed as stated until it has a depth equal to such radius. Or if weassume that the groove to be finished is a shallow one, in the exampleit is /32 inch, of less depth than the said radius, there will be nospecial difficulty, as by the tool holder not having room to clear thesides of the groove when it gets to the bottom of the shallow depth. Thespecial difliculty with small deep grooves will be further explained.The operation of the device thus generally described is to show that thedevice is adapted to dress the groove in the grinding wheel with greatprecision. It is useful for that purpose.

The device, however, is particularly adapted in a special way fordressing a grinding wheel with one or more small grooves, those grooveswith a small radius and relatively deep or deep enough to cause troublewhen the operation is only on the order of that above described. Thetrouble referred to is the difliculty in getting the tool holder. toclear the sides of the groove being dressed.

The device is adapted to do such particular work by the provisions nowto be explained.

The swinging arm or support 6 has two stops l8, one on each side. Theycooperate with adjustable stops l9 one on each side of frame part 8. Thelatter has a shelf 20 for each stop 19. A convenient construction forthis is to thread stop l9 through shelf 20 and supply a lock nut 2| tohold the vertical adjustment of stop l9. By loosening nut 2|, stop l9,screwed in shelf 20, may be given an accurate adjustment by a screwdriver applied from the top and nut 2| then tightened. Thus the lengthof the arc in which arm or support 6 may swing is limited by these stops[8 and I9. This limited length has reference to the operation alreadydescribed. That operation if tried out to make a full semi-circulargroove of /32 inch radius would run into the difficulty beforementioned.When the groove being dressed gets'near its full depth there is not roomfor the tool and its holder to clear the sides of the groove. This willbe seen from Fig. 9, using center C of cylinder 1 for swinging the tool.So the length of the arc is determined by the stops to prevent thecontinued mode of operation above described and just before the toolwould otherwise fail to clear the sides of the groove being dressed.

When the first way of operation is thus stopped, the device willautomatically change its way of operation to continue the dressing. Thesecond stage or modified operation is for the purpose of continuing thedressing of the small groove without any interference by the sides ofthe groove in clearing the tool. This will now be explained.

Up to the time that the tool will continue to dress the small groove toa gradually increasing depth without needing an are greater than thatdetermined by the stops, th cylinder 1 and shaft ii] are rocked as aunit by handle I! (Figs. 6 and 7). When the stops are engaged, handle IIcan by some extra force continue to rock cylinder 1 alone and furtherover on each side (Fig. 8). The stops act to prevent shaft I0 rocking asbefore with cylinder 1 and as if these two pieces were one. The frictionclutch and its detent construction, holds them together, as if they wereoneuntil the stops cause the clutch to slip. Then cylinder 1 can movewithout carrying shaft l0 and its tool support 6 in the way it did inthe first way. The detent I5 is moved out of its groove l6 (Fig. 8) whenhandle I! moves cylinder 1 after stops I8, I9 are engaged to stop shaftl0. Cylinder 1, however, carries shaft in and its arm 6 in a new way forthe second stage. This new way is to carry shaft l0, support 6, and thetool rods 2 and 3 bodily as a unit, but not on C as the center. When itsfirst stage movement with cylinder 1 is stopped, the cylinder movementis continued. Asshaft l0 cannotcontinuein thee oldaway-thecylinder mustcause the shaft ID to: move .in'a new way. The .frictionclutchconnesting. these-two parts; cylinder! and shaft l0; permits arelative movement between them;- This imoyement isone of relativerotation of shaft:

in the oifset bore I I of cylinder-1'." The latter of. course continuesits movement=on its own axis.

The relative rotation of shaftlfl in its offset bore,-

or-bearing, of course, is on theaxis of such bearing. Such relativerotation causes'the axisof shaft in to move downwardly onan arc. partsconnected with shaft. ID; that is swingingzarm or support 6, the toolholder rods'2 and 3,

and .thendiamond point tool. all move downwardly; This is indicatedbetween full and dotted lineipositionsin Fig. 9. In this movement-thediamond point is still being swung on the center 1 Cof' cylinder 1, over-its:cutting are as before. Its tool holder is being translated bodilyin a path aswell as the diamond point all take the downward path. Thisis the pathirequired for the diamond point to finish cutting thesemi-circular" or other deep groove by small increments and for thetoolholder toclear the sides of the groove. This result follows: because thetool holder is drawn'down out of the wayas the diamond point is .held tothe line of work, see Fig. 9. This line is: the continuation of the:same are started by merely swinging the tool on the one center C. Inthe.deep type of small groovesuch mere swingirigis stopped automaticallyjust before the point of the arc, where the tool holderwill interfere.Then as stateduthe diamond point and its tool diamond point follows tofinish the-arc shaped cut.

Reference toFig. 9 will indicate-the operationfroma more technicalviewpoint.

The are of the dressing within the angle'D, is the same as-the are madein the first way of oper- The down zthework againstthe tool.The-cylinder- H and shaft 10 will be: moved to' make exactly the rightare in the dressing.

'20 and every point of shaft iifl' varm 6, rods 2 and 3,

'35 holder is given a translatingmovement in which all parts are drawndownwardly, while the ation swinging the diamond point back and forthfrom center 0. When, the wheel is dressed with? such an arc and to thedepth of'its center from its chord, the way of'operation' is changed.It'is assumed that the .ends of said are represent the Now it will beseen from ;Fig.'c9 that the im portant thing is forthediamondpoint I tocontinue-to swing over the same are as before and extend the arc to makethe dressing deeper. It will also be seen that if the whole operationwere attempted by swinging the tool holder on center C the tool sideswould engage the work and interfere with maln'ng the deep small groove.It will finally be seen that this is prevented by a bodily movement ofthe tool sides downwardly and away from the groove while the diamondpoint is moved along the extended portions of the are beyond the sidesof angle D in Fig. 9.

In this respect the device automatically changes its way of operationbetween the first and second dressing parts of the whole operation tomake a small deep groove. All the operator need do, after the originalsetting of the device as in Fig. 1, is to swing handle I! back and forthand feed Within a considerable-scope; the radius of the i groove tobe-dres'sed may-be changed andthe same device used; That is the sameparts may beused to make difierent size grooves except the partrepresented by cylinder 1. This" cylinder 1 of the example is speciallymade for a roove of inch radius- The cylinder alone controls the-groovesize as-all the other parts are adapted for use in making differentsizes; when a differ-- ent size groove is wanted, another cylinder-issuppliedr It is in all respects like cylinder l except for the amount ofoffset between its axisand theaxis of thebore l Ithrough the cylinder;see Fig; 5. This offset is made different and to' correspond with thedifferent radius wanted for" the groove to be dressed. It would bemadeg.inch or /8 inch to make a groove smaller than the example of '3 inch.Thedevice described with a set of similar cylinders corresponding to"groove sizes wanted is the way in which the"- device would be put intothe shop. The frictionclutch parts i2 and M are readily removablefrom'shaft it. Supporting arm 6,shaft l0, and

cylinder 7 are readily removable from thefram'e' as" a unit by movementtothe right in Fig. 1. Then one cylinder such as I with one positionofoffset bore 5! may be substituted for the cylinder with a differentlypositioned offset'bore H', and the parts reassembled to make a differentsize groove'tha'n before. 7 While a good deal of description oftheideviceand its use seems de-' sirable for its disclosure, there arenot many parts, there are. no real complications, and the whole deviceis economical for manufacture and adapted for use in precision dressingofgrind ing wheels. The only'skill required is that of'pre- 'cision insetting the parts for work and that is plain measurement skill. Theoperation after it is once set up does not require skilL-but the mereswinging of handle H and the intermittent feedof the work holder betweencutting steps.

In the operation above described I considerthe function of detent idandgroove it very l helpful. When handle Ii has swung overfor stop it onsupport 6 to engage stop is; the engagement occurs as thearc of angle D,Fig. 9, 1

is finished. As handle 1'! swings further'o-ver' the arc is extendeddown to the end as seenin Fig. 9. In this movement of the tool from fullto dotted line positions the tool holder 2-3 is not swinging on point C.

whole are to the other corner, it is important to start swinging thetool holder 23' on center C about when it reaches full line position ofFig; 9'. 1

Otherwise the tool sides would begin to inter-- fere with the work. The'tool holder begins to swing on center C in the dressing operation fromleft to right as the holder reaches the full line position shown. Thisaction is insured by detent I5 engaging in groove I5 at just about thistime. Then the parts, shaft l0 and cylinder 1. will not slip relativelyas they might otherwise do and miss the time for beginning the swing oncenter C to do the work right.

Having disclosed the invention I claim:

1. A device for dressing grinding wheels, comprising a cylindrical bodyprovided with an end to end cylindrical bore with the axis of the boreoffset by an amount equal to the desired radius of a groove to bedressed in a grinding wheel and said axis also parallel to thecylindrical body axis, a tool support to hold a cutting tool point onthe axis of said bore to swing in aplane at right angles to the line ofsuch axis, a shaft mounted in said bore and carrying said tool supportfor its swinging movement, a frame with bearing means to mount saidcylindrical body, means to rock the cylindrical body about its axis tomove the axis of said shaft in an are having a radius equal to theamount of the shaft axis offset from the cylindrical body axis.

2. A device for dressing grinding wheels, comprising a cylindrical bodyprovided with an end to end cylindrical bore with the axis of the boreoffset by an amount equal to the desired radius of a groove to bedressed in a grinding wheel and said axis also parallel to thecylindrical body axis, a tool support to hold a cutting tool point onthe axis of said bore to swing in a plane at right angles to the line ofsuch axis, a shaft mounted in said bore and carrying said tool supportfor its swinging movement, a frame with bearing means to mount saidcylindrical body, means to rock the cylindrical body about its axis tomove the axis of said shaft in an are having a radius equal to theamount of the shaft axis offset from the cylindrical body axis, saidcylindrical body, shaft, and frame being readily separable so as tosubstitute a similar cylindrical body with a bore having another amountof offset from the body axis to change the radius of the are formovement of the shaft axis.

3. A device for dressing grinding wheels, comprising a cylindrical bodyprovided with an end to end cylindrical bore with the axis of the boreoffset and parallel to the cylindrical body axis, a tool support to holda cutting tool point on the axis of said bore to swing in a plane atright angles to the line of such axis, a shaft mounted in said bore andcarrying said tool support for its swinging movement, a frame withbearing means to mount said cylindrical body, means to rock thecylindrical body about its axis to move the axis of said shaft in an archaving a radius equal to the amount of the shaft axis offset from thecylindrical body axis, friction clutch means normally preventingrelative turning movement between the cylindrical body and the shaft,stop means adapted to limit the length of arc in which the cylindricalbody and shaft may rock as a unit and means including said stop means,adapted to permit a further rocking movement of the cylindrical bodybeyond the ends of such are to cause relative turning movement of theshaft in its offset bore While maintaining the axis of such shaft on theline of the limited are as extended beyond its aforesaid limited length.

4. A device for making annular grooves on the circular face of a disc,said device comprising a frame with a vertical portion having ahorizontal bearing, a precision made cylinder mounted to rock in saidbearing, a radial handle on the cylinder to rock it, a shaft mountedwith its axis precisely offset from the axis of the cylinder andextending through the cylinder for rotation, a friction clutch mountedbetween the shaft and cylinder and adapted to normally prevent suchrotation, and to permit movement of said handle to rock the cylinder andshaft as a unit, a tool support-connected to said shaft having means tohold the point of a cutting tool exactly on the axis line of said shaft,cooperating stops on said frame and tool support, such stops beingadjustable to determine the limits of a rocking movement of cylinder andshaft without relative rotation, whereby upon extended movement of saidhandle said clutch slips for the cylinder to rock further and for theshaft to be turned relatively to the cylinder whereby the shaft axis andsaid cutting tool point can continue to describe an arc of the sameradius and the tool support can be moved bodily to direct the sides ofthe tool into positions which will not interfere with the cuttingoperation substantially as described.

5. A device for the purpose described comprising a frame having ahorizontal bearing, a cylindrical body to swing over a long are aboutits own axis in said bearing, a shaft mounted in a corresponding borethrough said cylindrical body to act as a bearing for the shaft to turnin said body with the axis of said shaft and its bearing being parallelto and offset above the axis of said cylindrical body by an amount equalto the desired radius of a groove to be dressed in a grinding wheel, atool support mounted on said shaft adapted to hold the point of a toolon the axis line of said shaft, a handle to swing said body, a frictionclutch mechanism connecting said cylindrical body and said shaft tendingto resist relative movement of said shaft and body for them to sometimesswing as a unit and sometimes slip relatively to one another, saidmechanism including a notch and cooperating detent to help resistagainst such movement, cooperating stops to cause slipping in saidfriction clutch mechanism when the handle is operated to complete theportion of the said long are in the swinging arc of said body adjacenteach end of said movement.

WILLIAM WALTER HOPKINS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,312,347 Madsen Mar. 2, 19432,372,732 Norris et a1. Apr. 3, 19 5

